Genoa is a city riven by factionalism, between patricians (the nobility) and plebeians (the common people).

The plebeians Paolo and Pietro discuss the election of the city’s next leader. Paolo suggests the corsair Simon Boccanegra, who has protected Genoese waters against piracy. Paolo promises Pietro wealth and influence if he will persuade the people to elect Simon as Doge.

Simon is in love with Maria, daughter of Jacopo Fiesco. The Fieschi are a leading patrician family and enemies of Boccanegra. Maria is confined to the Fieschi palace because she had an illegitimate child with Simon. Paolo tries to persuade Simon that it would be difficult for the Fieschi to deny his union with Maria if he were Doge. Simon reluctantly agrees to Paolo’s suggestion. Pietro and Paolo persuade the people to back Simon in the election.

Fiesco emerges from the palace, lamenting Maria’s death and cursing Simon for seducing her. He does not tell Simon that Maria has died and denies Simon’s pleas for pity. He will not pardon his offences against the Fieschi unless Simon hands over the child he had with Maria. But Simon explains that she is not in his care: she was brought up in concealment by a woman who subsequently died. Thereafter the child vanished.

Simon enters the palace and discovers Maria’s body. Moments later voices are heard acclaiming him Doge. Simon is distraught at Maria’s death; Fiesco is outraged that his enemy, a plebeian, now has power.

25 years later…

Scene One

Simon and Maria’s daughter, also named Maria, was adopted by a patrician family, the Grimaldis, who named her Amelia. Her guardian is Jacopo Fiesco, who has assumed the name of Andrea Grimaldi and is unaware that Amelia is in fact his granddaughter Maria.

Amelia is in love with Gabriele Adorno, a nobleman whose father was killed by Doge Boccanegra. Gabriele asks for Fiesco’s permission to marry Amelia and is undeterred when Fiesco tells him that she is an orphan and not of noble blood.

Attended by Paolo, now his henchman, the Doge pays Amelia a visit. He brings with him a pardon for members of the Grimaldi family he has exiled. Amelia confesses that she is in love with Gabriele and tells the Doge the story of her childhood. He realises that she is his long-lost daughter and the pair celebrate their reunion.

Paolo also desires Amelia. When the Doge tells him to give up all hope of her, Paolo instructs Pietro to arrange her abduction.

Scene Two

The Doge presides over a session of the council, which is divided equally between patricians and plebeians. Paolo and Pietro are in attendance.

The Doge announces that he has received a letter from the poet Petrarch pleading for peace between Genoa and its rival Venice. To Simon’s dismay, the proposal is vehemently rejected.

The sound of civil disorder outside is heard. Inside, there is a standoff between patricians and plebeians. Voices are heard calling for the death of the Doge, who orders that the doors be opened. The mob bursts in with Fiesco and Gabriele. Gabriele announces that he has killed a man, Lorenzo, who abducted Amelia. Before he died, Lorenzo alleged that he was forced to commit the crime by a man of power. Gabriele assumes this to be the Doge and tries to attack him, but Amelia herself intervenes. She begs the Doge to spare Gabriele’s life.

Amelia relates the story of her abduction and escape and says that the man behind the plot is in the room. Violence threatens to erupt between the patricians and plebeians who accuse each other of the crime. The Doge calms the situation with an impassioned plea for peace. He rounds on Paolo, who he forces to curse the perpetrator of Amelia’s abduction. Paolo has no choice but to comply.

Fiesco and Gabriele have been imprisoned for their part in the rebellion. Paolo plots revenge on the man he helped to power. He laces the Doge’s drink with a slow-acting poison and also attempts to persuade Fiesco to murder him. Fiesco is outraged at such an ignoble course of action and Paolo has him returned to his cell. Paolo then turns his attention to Gabriele, stoking his jealousy by suggesting Amelia is the Doge’s mistress.

Gabriele confronts Amelia, who protests her innocence but does not reveal the truth of her relationship with the Doge. She hides Gabriele out of hearing as the Doge enters with a list of those who have conspired against him, including Gabriele. When Amelia confesses her love for the young patrician the Doge offers to pardon him if he changes allegiance. He dismisses Amelia and drinks the poison. Overcome with fatigue, the Doge sleeps and Gabriele is about to kill him when he is stopped by Amelia. On waking, he reveals that he is Amelia’s father and Gabriele begs forgiveness.

Sounds of a patrician revolt are heard. The Doge spares Gabriele’s life and sends him out with an offer of clemency. Gabriele swears to fight at the Doge’s side if it is refused.

The revolt has been defeated. Fiesco has been granted his freedom and Paolo condemned to death. He admits to Fiesco that he has poisoned the Doge. To the distant sound of Amelia and Gabriele’s wedding ceremony Paolo is led away to execution. 

The poison has taken effect. Fiesco approaches Simon, who is at last able to tell him that the child who was lost has been found. At this the two men are reconciled. Amelia and Gabriele arrive and, with his dying breath, Simon blesses the couple and names Gabriele his successor. Fiesco proclaims Gabriele Doge.